Conventionally, there is a system in which a personal computer (which may be abbreviated as a PC hereinafter) serves as a host, and peripheral equipment such as a reading apparatus (scanner) capable of reading an original is connected to the PC to transfer the image data read by the reading apparatus to the PC and store it as a image file in the PC. In such a system, the PC generally has a hard disk drive as a large-capacity storage unit capable of storing several GB data. For example, since the image data obtained by reading an A4 original at 300 color dpi has a size of about 24 MB, there is no chance of a shortage of an area for storing image data on the system, and hence no problem is posed in terms of the arrangement of the system.
Recently, as a simplified version of the PC described above, a simple personal computer (which may be referred to as a hand-held PC hereinafter) has been developed, which has only a memory (RAM) generally capable of storing data of several ten MB as a storage unit in place of a large-capacity storage unit such as a hard disk drive.
If, however, the above reading apparatus is connected as peripheral equipment to the recently developed hand-held PC, since the size of data that can be stored in the hand-held PC may be smaller than the size of read image data, various problems arise, e.g., a problem associated with the operation performed by the user and improper storage of data obtained by reading operation. In a reading apparatus capable of reading color images, in particular, read image data must be processed in almost the same unit of size as the capacity of the memory (RAM) of the hand-held PC. This makes it difficult to realize a system that can improve user operability and satisfactorily implement the function of the above reading apparatus.
In consideration of such problems, a system capable of improving the user operability and satisfactorily implementing the function of the reading apparatus is disclosed in Japanese Patent Laid-Open No. 10-116339, “Image Reading System and Information Recording Medium”, filed by BROTHER INDUSTRIES, LTD. In this system, when image data to be read is larger than the available memory (RAM) capacity (corresponding to the free area of the data storage unit in the above reference) of the hand-held PC, the user operability can be improved and the function of the reading apparatus can be satisfactorily implemented by changing the reading setting (the reading condition in the above reference). However, the following steps are required to complete reading operation:                (1) setting an original;        (2) setting reading conditions;        (3) scanning the image;        (4) comparing the size of the image data to be read with the free area of the data storage unit;        (5) if the size of the image data to be read is lager than the free area of the data storage unit, changing the reading conditions to allow reading operation within the size range of the free area of the data storage unit (displaying the reading conditions after the change in a main window);        (6) scanning the image again; and        (7) terminating the reading operation.        
As described above, however, seven steps are required to complete general reading operation. That is, cumbersome operation is required.